The Conception of the Triboro Line

By the mid 1990s, subway ridership rose as the city’s population grew to more than 8 million, crime rates dropped, and the MTA eliminated subway tokens with the introduction of the quick-swipe MetroCard. Meanwhile, RPA was on the cusp of releasing our Third Regional Plan entitled ​“A Region at Risk” which was fitting since the plan was conceived before this revival was fully evident.

RPA’s series of transit recommendations in the Third Regional Plan, ​“A Region at Risk” were fleshed out by Jeffrey Zupan, RPA‘s then Senior Fellow for Transportation under the overall leadership of Robert Yaro, RPA’s Executive Director. These ideas were collectively known as the Regional Express, or RX vision. The Regional Express called for the restart of a full-length Second Avenue subway, first proposed by RPA in its first regional plan, published in 1927, ​“The Regional Plan and Its Environs.” This subway line was started and then abandoned in the early 1970s. Within that RX package of proposals was a new idea, Triboro Rx (now IBX).

Inspiration from Europe

In the 1970s, European cities were rethinking their own transit systems. Paris, in particular, implemented a model that piqued RPA’s interest in 1977. This was their ​“Réseau Express Régional” (RER) initiative that connected, through the city, discontinuous suburban segments of their transit network. It created a hybrid system in which commuter trains would operate more as subways as they passed through the city enabling an exponential increase in connectivity and one-seat rides across the Paris region.

RPA built on this idea, calibrating it to the legacy system already in place in the tri-state region. As in Paris, it would be a regional system with the same outsized potential for new regional connectivity. RPA studied all of the abandoned or lightly used rights-of-way throughout our region and discovered that this type of connectivity could be accomplished by patching relatively few gaps in the system and exploiting the existing rights-of-way, such as the LIRR Bay Ridge Branch, which is now the right-of-way for the IBX.

Through the rest of the 1990s and into the 2000s, RPA continued to keep this idea alive. RPA regularly analyzed and reported on the MTA’s Capital Program, sometimes warning that the MTA was slipping into a downward spiral. While RPA had higher priorities, such as the new trans-Hudson tunnels (Access to the Region’s Core or ARC at that time, now called the Hudson River Tunnel, part of the Gateway Program,) and the full Second Avenue Subway, the Triboro Line was always kept on the list.

During these years, and still today, RPA worked closely with Congressman Jerrold Nadler, whose concept of a revived seaport in Sunset Park depended on the rehabilitation of the Bay Ridge Branch for freight and completion of the Cross Harbor Tunnel at the Sunset Park waterfront where the line terminates. (The idea of a cross-harbor freight tunnel was also first conceived by RPA in the First Regional Plan of 1929). During the early oughts, RPA was focused on passenger service, but RPA recognized the value of the corridor for goods movement and so RPA supported Congressman Nadler’s efforts to reinvigorate the corridor.

By the year 2000, subway ridership largely recovered. In the years between the 3rd and 4th Plans (1996 - 2017), RPA continued to study and make the case for the Triboro Line. Using Census Journey to Work data, RPA estimated the potential ridership for the Triboro service, finding that the new service could serve well over 100,000 riders a day.

The Triboro in the 4th Regional Plan

In the 4th Regional Plan (2017), RPA recommended a series of ideas for transit access interconnectivity including a new ​“A Regional Express (RX)” system that combined the Long Island Railroad, Metro-North Railroad and New Jersey Transit into a unified system that would vastly improve mobility throughout the region. As in the 3rd Regional Plan (1996), the Triboro Line was once again included as a key circumferential connector that linked the otherwise disconnected transit lines as they converge in a radial pattern into Manhattan.

Designing the Potential IBX Corridor

As part of the Fourth Regional Plan, RPA worked with a series of architects and designers to explore the future land use and urban design implications of recommendations. The Triboro was one of four large geographies selected via a RPA sponsored competition, called 4C: Four Corridors design initiative.

The design team of OnlyIf and One Architecture were selected to imagine future land use change along the entire Triboro corridor. Their approach was to balance what they called Transformative Projects with smaller, neighborhood-scale interventions. The Transformative Projects were at the major intersections of the new surface transit line and multiple subway and commuter lines. Elsewhere they showed a local value-capture scheme in which the value-added by the new light rail was captured for the benefit of contextual infill development to reinforce the existing neighborhood character.

From 2017-2019, thanks to support from the New York Community Trust, RPA advocated for the Triboro concept, with a broader goal to build momentum for greater transit investment especially in the outer boroughs. Through events, meetings, media and letter writing campaigns, RPA worked with outer borough elected and community leaders to explain the potential for the new transit service. Many events were held in tandem with RPA’s advocacy around congestion pricing.

A strong proponent was New York State Assembly Member Latrice Walker, who introduced legislation in 2019 for the MTA to conduct a feasibility study of the Triboro line. At the same time, new leadership at the MTA, especially Janno Lieber, embraced the idea. The MTA began a feasibility study in 2021.

In 2022, Governor Kathy Hochul formally endorsed the idea of the Triboro in her State of the State address when she directed the MTA to conduct an environmental review for the project. The Governor renamed the project the Interborough Express and indicated that it would run between Brooklyn and Queens.

Since the MTA’s adoption, the IBX is only designed to run between Brooklyn and Queens. Largely due to the complexity of operating the IBX into the Bronx with competing regional rail service, that segment has been removed by the MTA. In the interim, the Bronx is on track to receive additional transit investments through the Bronx Local Bus Network Redesign and additional commuter service via the Penn Station Access project. However, RPA remains committed to advocating for additional service to the Bronx, as part of our continued call for expanded transit options in underserved parts of our region.

The MTA’s feasibility study for the project was released in early 2022 which confirmed the potential for a high-ridership, cost-effective corridor. In January 2023, the MTA selected light rail as the mode of transit.

While tunnel-boring transit projects such as the Second Avenue Subway extension are slow and expensive, the cost of building the IBX line will be considerably more affordable as it will use the existing freight rail corridor.

In summer of 2025, Governor Hochul joined MTA leaders Janno Leiber and Jaime Torres-Springer, elected officials, community leaders and transit advocates to announce the commencement of the design and engineering phase of the project.

This historic moment was made possible thanks to the fully funded $68 billion dollar MTA 2025 - 2029 Capital Plan, funded by the New York State FY 2026 Budget. The 2025 -2026 Capital Plan includes funding for $2.75 billion of the estimated $5.5 billion cost for the full line. This first allocation of funding will cover the majority of initial design, engineering, and construction to start building the IBX line. RPA will continue to advocate for the IBX to ensure the project is fully funded, once the preliminary design and engineering phase is completed.

Since the MTA’s adoption, the IBX is only designed to run between Brooklyn and Queens. Largely due to the complexity of operating the IBX into the Bronx with competing regional rail service, that segment has been removed by the MTA. In the interim, the Bronx is on track to receive additional transit investments through the Bronx Local Bus Network Redesign and additional commuter service via the Penn Station Access project. However, RPA remains committed to advocating for additional service to the Bronx, as part of our continued call for expanded transit options in underserved parts of our region.

In October 2025, the MTA began the Environmental Review process for what will be the city’s first light-rail system. As we learn more about the potential challenges and continued opportunity presented by this system, RPA will continue to be an important voice in promoting the need for its completion. In 2026, RPA will host public events to engage with the diversity of stakeholders along the route and to help educate the general public about future project benefits.

RPA will host a business roundtable, centered around businesses who may be directly impacted by the construction of the IBX, as well as businesses that are currently serviced by the freight line, and businesses that stand to benefit from future accessibility that the IBX will provide. RPA will also host a public conversation about what light-rail transit means for New York City. Even though the IBX will add a new mode to the MTA’s system, light-rail transit has long been operational in cities both near and far. Through this conversation, RPA will provide an opportunity for global experts to share their best practices for this mode, learn what is needed to avoid pitfalls from similar projects, and how to maximize benefits for future riders.

The IBX will take some time to build and continued support for this project is key. It is the only system expansion project in the MTA’s 2025-2029 Capital Plan, and we know that challenges lie ahead. But it will unlock so much more than shorter commute times. The IBX will bring riders to new job opportunities, increase access to civic and educational resources, set the stage for much needed housing, encourage transit-oriented development, and provide direct connections for ethnic and cultural enclaves spread along the route. Building the IBX will bring more transit options for passengers in Brooklyn and Queens while ensuring that freight moves sustainably by rail. To maintain our region’s health, equity, prosperity and sustainability, the IBX remains an important component of our future.